These proved problematic:
I bought them at aliexpress.
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So the advice is to not buy chips that come on white foam? 
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Pretty sure I’ve never seen genuine TI chips with two dimples (and a notch!). Certainly not the TL074CN I currently have.
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Ha, ha, which reminds me of that early AI system I once read about that was capable of distinghuishing between US and USSR tanks … because the US tanks were parked in front of a wall which differed in color from the wall the USSR tanks were parked in front of.
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Same with AI trying to detect skin cancer from images. All the cancer images had also a ruler on them, it learned to detect the rulers, not anything on the skin.
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Not bad advice as the white foam may not be conductive and could cause static electricity to damage the chips.
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I’m pretty sure my fake TL074 are rebadged LM324 as they work fine on a single supply rail. So now I have stock of 100 LM324 chips.
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Not TL’s but still, none of them worked.
Luckily I had a positive so I could build a testcircuit which worked, but these turned out all to be negatives:
Familiar odd TI-branding …
Bought at aliexpress, I obviously disputed the delivery and …
the dispute was decided in my favour IMMEDIATELY (read: within a minute) after entering the dispute.
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The question is, if not LM3900, what are they? 
That’s strange lm324’s should be able to work on both singular or bipolar supplies. Did you find a use for these mystery opamps?
Yes they do work on both, but TL074 don’t which is how I graded them as lm324 equivalents. I use them on non important stuff where they are not pushed too much, there rail to rail performance is not as good as a TL074.
Blockquote
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I suspect they are quad opamps of some sort, but I don’t know. I will try them in a quad opamp configuration and report back.
[Edit] As I suspected, all are (working) quad opamps.
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Not a 100% certain yet, may be just a faulty part but I built a 3.3v regulator today with an lm317T, it’s a circuit I’ve built at least 10 times before so I know it well, but it was outputting 4.3v under load and about 4.6 off load, which is strange because normally it’s 3.328 volts approx every time on or off load. I bought a new batch of lm317t at the weekend, so it could be just one faulty chip. I’m going to build another tomorrow to test.
5v to 3.3v converter is all it’s doing.
I just build a compressor based around 2 074s and they turned out to be fakes, you could see a different texture to the top of the IC around the lettering, which was highlighted by flux gunk. Switched them out and the module sprung to life.
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DON’T buy chips on sBay
DON’T buy chips on AliExpress
DON’T buy chips from Chinese suppliers.
I have a large stock of chips I bought up to 40 years ago, fortunately, when fake chips were less of a ‘thing’.
However, I did once date a girl who told me her Mum worked for a semiconductor supplier in south London (who are still trading). Her Mum’s job was rubbing part numbers off components and printing new ones on. “Oh, aren’t you supposed to do that?” she asked after my sharp intake of breath.
Or DO. I’ve bought some perfectly acceptable chips on eBay and AliExpress.
But these were exceptional instances, they were ones I bought because I thought they’d be fun to have, not because I needed them, and I bought them knowing they might be crap and if so I could probably get a refund but should be prepared to eat the cost.
And I don’t buy when the price is absolutely way too good to be true. No one can get legitimate AD633 for a price low enough to resell them for anything like $5.
I get 99% of my ICs from more reputable sources.
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I have bought many many perfectly good chips from AliExpress over the last 5-6 years, only a small, less than 1% of fakes, I was especially pleased to get a DAC-71 used in the sequential circuits prophet 600 for $25. In fact out of all my purchases I think only 2 have been fake from AliExpress, others fakes have been sourced locally and I don’t know their origins, but I can guess at China.
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funny you should mention the ad633’s I bought the to good to be true ones once , just got very hot when plugged in . it sucks but the real ones are not cheap , think it was the MFOS ring mod I built that uses them .
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And the Befaco A*B+C uses two!
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